# Where do I find good IV curves?

I bought a couple components for a quick project and like to know all of the math behind the voltages / current / resistance before I hook stuff up. For example, I bought multiple vibration motors off Amazon. They are small and cheap, but I cannot find any IV curves. https://www.amazon.com/tatoko-Vibration-Button-Type-Vibrating-Appliances/dp/B07Q1ZV4MJ/ I look through this and find only "DC 3V". On other products which look the exact same with DC 3V, I find that it pulls 80mA at 3v.

How is one supposed to find a reliable IV curve before you buy? What if my project requires it to be only 20-40mA? Just like an LED, I may want different intensities (not counting PWM).

Is the IV curve the right thing to be looking for, or is there some underlying database that I am looking for? Thanks for the input on how you find what to use.

• Well IV curves are for components, such as RLC. On the other hand, vibrator is a circuit, or a device, which has a spec, such as this: Vibration Motor, 3V, 85mA,12000rpm. Of course you can DIY an IV curve, but no body is interested to know if 3V 70mA OK, 2.5V 50mA half OK, 2V don't work etc.. Commented Nov 13, 2020 at 5:06
• Buy quality kit from reputable suppliers and get data sheets - cheap stuff often lacks (good or any) documentation. Commented Nov 13, 2020 at 5:30
• @tlfong01, you don't need IV curves for RLC components because they are linear. You need them only for non-linear devices such as diodes and transistors which are non-linear. Commented Nov 13, 2020 at 7:23
• @tlfong01, it's linear and easy. $V_C = IZ_C$ and $V_L = IZ_L$. Commented Nov 13, 2020 at 9:11
• What to check for when buying an electronic component or module? Commented Nov 13, 2020 at 10:19

You may not be able to find data on that part, though if you do need to use it in an "unusual" mode you might search for a part that is specified for that service.

For example, here is a datasheet for a similar device.

The only specifications given are that the current is guaranteed to be 80mA or less at 3.0V, recommended operating range is 2.5 to 3.5V and it is guaranteed to start as low as 2.3V (but only if you step the voltage to the motor, you're not allowed to sneak up on the voltage). That has probably been adequate information for them to sell millions of the devices at very reasonable prices.

If you are willing to pay a "bit" more Precision Microdrives offers a similar sized product with these typical performance characteristics:

It is anyone's guess whether those curves bear any similarity to the Amazon product or the Seeed product. There are also no guarantees, but it should give some rough idea of how it behaves.

• Ah, your product sheet is very good. Usually I googled the website of the factory of the product and order direct from the so called flag ship shop or authorized dealer in from TaoBao. Usually the shops and factories are based in ZhenZhen or nearby provinces in South China (Some very high tech, military, space) are based in Beijing, or near the cities where the space ships etc are fired. Some products are marked "space grade". Often I trace to the AliBaba B to B guys (not AliExpress for hobbyists) who give datasheets in every detail. Commented Nov 13, 2020 at 7:03
• "Typical" data is useless unless you know the tolerances either side of "typical". Commented Nov 13, 2020 at 16:17
• @alephzero For analog parts you usually don't have guaranteed tolerances from the manufacturer except at a few points, and often you only have minimums or maximums guaranteed even there. The usefulness of the typical data shown above is that it tells you the motor will stall below some particular voltage, and above that voltage the current, frequency and amplitude increases more-or-less linearly. That helps in interpreting the guaranteed starting voltage. Where one can get into trouble is if one assumes that it will start at the 'typical' voltage or that the curves are quantitatively accurate. Commented Nov 13, 2020 at 16:41

/You may or may not have luck with finding specs as you have seen. Other potential sources of information include developing familiarity with what is likely to be in the ballpark due to experience e.g. LEDs small forward voltages, 5mA and up to light; searching for parts by analogy e.g. a similar product you found on another site; review of other documentation e.g. schematics for similar project and datasheets; and of course plain "suck it and see" experimentation.

Speaking of databases you might want to familiarise yourself with component websites such as Mouser, Element14, RS Components as they have searchable portals where you can specify searches on voltage, current, frequency, power, ...

• Ah, you remind me that once I was curious about a blue LED, and I searched for the Taiwan factory site which give the data sheet of ALL their product lines of LEDs in different colours (wave lengths). They are commercial sites are open to public, so poor hobbyists like me can visit their site and learn new things. Commented Nov 13, 2020 at 7:07
• @tlfong01 I remember when Blue LEDs first became available and they cost 200x more than a Red LED... Commented Nov 13, 2020 at 9:40
• Really? I always thought that blue LED has always been as dirt cheap as red LED. But I have always been so jealous of the three Japanese guys getting a Nobel Prize just by "easily" "dyeing" red LED to into blue LED. (1) Invention of blue LEDs wins physics Nobel, By Jonathan Webb, Science reporter, BBC News, 2014oct07 bbc.com/news/science-environment-29518521. Ah, locking down supper time. See you guys later. Cheers. Commented Nov 13, 2020 at 9:52